pass object or use self.object?

Jean-Michel Pichavant jeanmichel at
Tue Apr 6 11:19:06 EDT 2010

Tim Arnold wrote:
> Hi,
> I have a few classes that manipulate documents. One is really a
> process that I use a class for just to bundle a bunch of functions
> together (and to keep my call signatures the same for each of my
> manipulator classes).
> So my question is whether it's bad practice to set things up so each
> method operates on self.document or should I pass document around from
> one function to the next?
> pseudo code:
> class ManipulatorA(object):
>     def process(self, document):
>         document = self.do_one_thing(document)
>         document = self.do_another_thing(document)
>         # bunch of similar lines
>         return document
> or
> class ManipulatorA(object):
>     def process(self, document):
>         self.document = document
>         self.do_one_thing() # operates on self.document
>         self.do_another_thing()
>         # bunch of similar lines
>         return self.document
> I ask because I've been told that the first case is easier to
> understand. I never thought of it before, so I'd appreciate any
> comments.
> thanks,
> --Tim
Usually, when using classes as namespace, functions are declared as 
static (or as classmethod if required).

class Foo:
    def process(cls, document):
        print 'process of'

    def foo(document):
        print document

In [5]: Foo.process('my document')
process of
my document

There is no more question about self, 'cause there is no more self. You 
don't need to create any instance of Foo neither.


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